The present invention relates to a metal gasket for an internal combustion engine, more particularly a metal gasket with a bead having pressure adjusting portion to adjust pressure applied to the bead.
A metal gasket is installed between two engine parts, and is tightened by a plurality of bolts therebetween. Since the bolts are not arranged equally over the entire area of the engine parts, the tightening pressures applied onto the gasket by the bolts are partly different.
Especially, in a cylinder head gasket, the bolts are arranged around cylinder bores to seal therearound by sealing devices as equal as possible. Although other sealing devices are formed around other holes, such as water holes and oil holes, the sealing pressures for other holes are not generally considered. Even if the sealing pressures for other holes are considered, since many other holes are formed outside the cylinder bores, the other sealing devices can not receive substantially equal tightening pressure from the bolts. Therefore, although the sealing devices are desirably tightened as equal as possible, the sealing devices are not equally tightened.
In order to solve the above problems, U.S. Pat. Nos. 5,149,110, 5,269,541 and 5,344,165 were proposed, wherein the spring constant of the beads formed around the fluid holes is changed with reference to the location of the fluid holes and the beads in the gasket.
In U.S. Pat. No. 4,759,556, a bead between two bolt holes is provided with an auxiliary bead to increase surface pressure between the two bolt holes, i.e. two beads are partly formed. Therefore, the surface pressure of the bead at the portion between the two bolt holes can be increased.
The prior patents as explained above operate generally as intended. However, it is still desirable to improve the gasket.
On the other hand, in case a surface pressure of a gasket is partly increased, a surface pressure regulation plate or small tip of a plate is piled on the gasket. In this respect, it is desirable to provide a device to easily adjust surface pressure of the gasket.
Accordingly, one object of the invention is to provide a metal gasket with a bead, wherein the bead can widely support a pressure applied thereto.
Another object of the invention is to provide a metal gasket as stated above, wherein the bead can provide an extra surface pressure where high pressure is applied.
A further object of the invention is to provide a metal gasket as stated above, wherein creep relaxation of the bead is prevented.
Further objects and advantages of the invention are apparent from the following description of the invention.